Mechano-chemical surface modification of calcite by wet-stirred ball milling

摘要

In this study, surface modification of calcite was examined using a laboratory stirred ball mill in we condition. A fatty acid collector, sodium oleate (oleic acid sodium salt), was used as the modifying agent. Surface modification of the ground calcite sample was studied as a function of sodium oleate dosage, time and pH. Modification efficiency was mainly evaluated by floating test, which measures the active ratio. The effect of surface modification was also investigated using thermogravimetric (TG) and fourier transform infrared spectrometry (FT/IR) analyses, and contact angle measurements. Furthermore, mineralogical and microstructural changes were determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The results indicated that hydrophobicity of the powdered calcite increased with increasing sodium oleate dosage, in which the active ratios of 99.0% and 100.0% were obtained with the dosages of 5.0 and 7.5 kg/ton, respectively. Beyond this point, the active ratio values decreased dramatically down to 33.63% for 15.0 kg/ton. Similarly, hydrophobicity values increased with modification time up to the active ratio of 99.27% for 11.5 min. Different to the modifier dosage, additional time resulted in only a very small decline and the active ratio decreased down to 97.70% for 20 min. The best result of 99.27% was obtained with the natural pH of about 9, and the active ratio values substantially decreased below and above this point down to 38.07% for pH 6 and 47.32% for pH 12. Overall results have shown that natural hydrophilic calcite can easily be made hydrophobic using sodium oleate as the surface modifier.